在散点图旁边显示颜色编码的图例

Question

Looking at this code:

pairs(Iris[1:3], main = "Anderson's Iris Data -- 3 species",
pch = c(21),  cex = 2,bg = c("red","green3","blue")[unclass(iris$Species)])

is it possible to show the groups/classes Species as legend color coded?

Answer 1

pairs(iris[1:3], main = "Anderson's Iris Data -- 3 species",
      pch = c(21),  cex = 2, bg = c("red","green3","blue")[unclass(iris$Species)], oma=c(4,4,6,10))
par(xpd=TRUE)
legend(0.55, 1, as.vector(unique(iris$Species)),  fill=c("red", "green3", "blue"))

From ?pairs: Graphical parameters can be given as arguments to plot such as main. par("oma") will be set appropriately unless specified. Hence any attempts to specify par before pairs will result in override.

Additionally it is very complicated to control the legend position in pairs .

I recommend using library(GGally)

library(GGally)
ggpairs(iris, aes(color = Species), columns = 1:4)